Cable television systems provide a method of television signal distribution between a central facility generally referred to as the "headend", and a large number of television viewers through a cable distribution system. The headend includes the source of programming information together with a plurality of television channel modulators which provide a plurality of television program signals at different channel frequencies. The plurality of program channel signals are communicated to the individual television viewers via a network of cables, distribution equipment, and individual signal decoders at each user location. Early cable television systems were usually limited to one-way cable systems so named because all communication occurred from the headend down through the system to the individual decoders. Later developed systems provided communication capability in both directions between the headend and encoders and are thus referred to as two-way cable television systems. For purposes of convenience, communications and information transmission from the headend to the user decoders is generally referred to as "downstream" communication while the transmission of information and data from the user decoders to the headend of the system is referred to as "upstream" communication.
Downstream signals or communication typically include program information together with appropriate television scan synchronizing information plus additional data such as subscriber addresses or program authorization. This additional data is usually combined with the program information during the vertical blanking interval of the signal. Typical upstream signals or information may include program purchases or other relevant information such as responses to status inquiry or polling information requests.
In most cable television systems, the various program channels are grouped into basic service channels together with special optional channels which require additional service fees or payments to be received by the viewer. The latter are generally referred to as channels or programs and may be received and displayed solely by those decoders within the cable system which are authorized to view them. In virtually all cable television systems, the need for authorization to receive and display pay per view programming is enforced by the use of scrambled signals on pay per view channels. At the headend of the system, a signal scrambler is operative upon the program information to alter it in a manner rendering it virtually unviewable when applied unchanged to a television receiver. At the decoder, a corresponding descrambler is operative to unscramble the program information and return it to the proper television format for viewing on a conventional television receiver. The headend further includes an address computer and signal encoder which cooperate to insert the program authorization information for the pay channel within the vertical blanking interval. Correspondingly, the encoder includes systems for responding to the authorization information within the vertical blanking interval to activate the descrambler once the proper authorization signal is received.
When a cable television viewer attempts to receive a particular program channel, the encoder is tuned to the selected channel and the encoder determines whether the appropriate authorization code is present during the program signal vertical blanking interval. The presence of the appropriate authorization code indicates that the decoder is authorized to receive the pay program information and the descrambler is activated and the program information is properly displayed. If, however, the correct authorization code is not carried within the program signal, the decoder is not authorized to receive the pay per view program and the signal will not be descrambled. In some cable television systems, unauthorized pay programs are simply displayed in their scrambled form and are thus unviewable. In other systems, however, a viewer request for an unauthorized pay signal causes the decoder to be switched to an alternate channel which provides additional information to the viewer. Such alternate channels are generally referred to as "barker" channels and the process of automatically switching to such alternate channels is generally referred to as "barkering". In their simplest form, barker channels may simply display information to the viewer indicating that the viewer is not authorized to receive the selected program and may suggest that the viewer subscribe to the pay channel.
In some cable television systems, the viewer, having selected an unauthorized program channel, is afforded the opportunity to obtain authorization immediately in a process often referred to as individual or impulse pay per view. In one impulse pay per view system, the barker channel instructs the viewer to utilize a conventional telephone to call the cable headend and thereby obtain authorization. In other cable television systems having two-way communication, the barker channel may instruct the viewer to respond appropriately by using the upstream communication of the cable television system itself.
Once the user has responded appropriately in the impulse pay per view situation and obtained authorization, the user then switches the decoder back to the selected program channel and attempts again to receive the desired program information.
While the present barkering systems provide some benefit in cable television systems and facilitate individual or impulse purchasing of pay per view programming, they remain subject to several problems and limitations. Perhaps the most significant arises out of the timing required on the part of the viewer to carry out the impulse purchase. For example, in the event the viewer attempts to return to the selected program channel from the barkering channel too quickly, the program authorization may not have been completed resulting in return to the barkering channel and viewer confusion. By way of further example, in the event the user attempts to return to the selected program channel while authorization is taking place, the necessary communication link between the decoder and the headend is interrupted and authorization may again fail. In some two-way systems, the requested transaction is implicitly identified by the channel tuned. In such systems, correct identification of the desired program would require the use of a separate barker channel for each pay per view program. This would increase costs and complexity of the barkering system.
Accordingly, it is a general object of the present invention to provide improved cable television system barkering. It is a more particular object of the present invention to provide improved cable television system barkering which is more user friendly to the viewer and which minimizes confusion of the viewer.